In general, a track-guided vehicle (hereinafter referred to as a “vehicle”), such as a subway car, or a new transportation system vehicle, runs along a track while being guided by a guide rail arranged along the track. In a wheel truck of a conventional vehicle, a running wheel of a rubber tire, or the like, is arranged facing in a fixed direction at all times relative to a guide wheel guided by the guide rail. Therefore, the direction of the running wheel is changed only by following the guide rail. However, when the vehicle moves into a curved guide rail, a large guide wheel working force directed toward the guide rail is applied to the guide wheel due to a force generated by the running wheel traveling straight or a centrifugal force acting on the vehicle. The guide wheel and the guide rail are thereby brought into contact with each other at a great pressure. As a result, there occurs a problem in that wear and deterioration are easily caused on the guide wheel and the guide rail.
To solve the problem, a cornering force on the running wheel opposing to the guide wheel working force, is increased, to thereby reduce the contact pressure of the guide wheel and the guide rail. As a method of increasing the cornering force, a steering mechanism for steering the running wheel is provided in the wheel truck of the vehicle, and the running wheel is steered by the steering mechanism so as to increase a slip angle (a steering angle) when the vehicle moves into the curved guide rail.
A wheel truck including such a steering mechanism is disclosed in Patent Document 1. In Patent Document 1, a pair of running wheels is connected to each other by an axle so as to be rotatable by a kingpin, and can be also interlocked with each other by a tie rod arranged along the vehicle width direction. Meanwhile, a guide wheel guided by a guide rail is mounted to a guide frame, and the guide frame can be turned around the center position between the pair of running wheels relative to the axle. Furthermore, a steering rod, for steerably connecting one of the pair of running wheels to the guide frame, is arranged along the vehicle width direction. One end part of the steering rod is mounted to a steering arm for steering one of the pair of running wheels, and the other end part of the steering rod is mounted to the guide frame so as to be movable in the vehicle front and rear direction. In addition, an actuator, which is extensible and retractable in the vehicle front and rear direction, is provided on the guide frame, and the end part on the guide frame side of the steering rod is mounted to the actuator. By the movement of the end part on the guide frame side of the steering rod along with the operation of the actuator, the distance between the end part and the turning center of the guide frame (or the axle) is changed relative to the distance between the end part on the running wheel side of the steering rod and the axle, so that the steering rod adopts a posture tilting relative to the axle. As a result, the displacement of the steering arm changes with the movement of the steering rod, and therefore, the slip angle of the running wheel steered by the steering arm is changed.